The proposed study is designed to improve assessment techniques currently available in the substance abuse field by establishing the psychometric properties of screeners for trauma history and for trauma-related psychological symptomatology, specifically post-traumatic stress disorder (PTSD). It will assess the utility of these screening measures for predicting treatment retention and functioning and further expand our knowledge of the relationship of trauma to the current functioning of methadone clients. The specific aims of this study are: (1) to test the reliability and criterion validity of screening questions for assessing history of traumatic events in a methadone treatment population; (2) to establish the reliability and criterion validity of a self- report screening instrument for PTSD in a methadone treatment population; and (3) to examine the predictive validity of these screeners for determining current functioning, treatment retention, and treatment outcome in a methadone treatment population. Reliability of the screeners will be examined in two ways. First, internal consistency reliability will be assessed using coefficient alphas computed from the baseline assessments of a sample of 200 methadone treatment clients. Second, stability over time will be assessed by computing test- retest reliability coefficients, i.e., the correlation between the scores on the screeners at baseline and at a second administration 7 to 14 days later. Validity of the screeners will also be examined in two ways. To assess criterion validity, a sample of 120 TEP participants will be selected to undergo a Gold Standard Diagnostic Battery following their routine baseline assessment. This battery, a semi-structured clinical interview that will be administered by trained clinicians, will contain "gold standard" assessments of lifetime exposure to trauma and a PTSD diagnostic assessment. Criterion validity will be assessed as the correspondence between the screeners and their respective gold standards in terms of sensitivity, specificity, positive and negative predictive power, and the Kappa statistic. To assess predictive validity, scores on the screeners will be correlated with measures of treatment needs, client functioning, and retention in treatment to determine whether the screeners are related to these other important indices. The ability of the screeners to predict retention, and to predict client functioning in a variety of domains, is important to their ultimate utility in treatment settings. Retention and quarterly follow-up data that are routinely collected as part of TEP will be used in these analyses.